Fine symbol timing synchronization method and apparatus in ofdm system
AssigneeALi Corporation
InventorYu-Ting Xu
Life of this patent
Estimating the term…
Abstract
A fine symbol timing synchronization method and apparatus in an orthogonal frequency-division multiplexing (OFDM) system are provided. The fine symbol timing synchronization method finds a path with a minimum mean square error (MMSE) as a first path among a plurality of paths, and a formula of the mean square error (MSE) used by the method is a simplified formula of the original MSE formula with low calculation complexity. Therefore, the time required by the fine symbol timing synchronization method is short, and a correct first path can be found, so as to lock a starting position of a fast Fourier transform (FFT) window on a starting position of a symbol signal of the correct first path.
Claims20
A fine symbol timing synchronization method in an orthogonal frequency-division multiplexing (OFDM) system, comprising:
- receiving a plurality of first time domain symbol signals;
- performing a fast Fourier transform (FFT) on the first time domain symbol signals to generate a plurality of first frequency domain symbol signals;
- extracting a plurality of scattered pilots from the first frequency domain symbol signals, and calculating a plurality of first channel frequency responses according to the scattered pilots;
- performing an interpolation on the first channel frequency responses to generate a second channel frequency response;
- storing one of the first frequency domain symbol signals, wherein the stored first frequency domain symbol signal is corresponding to the second channel frequency response;
- performing a zero padding operation on the second channel frequency response, and performing an inversed fast Fourier transform (IFFT) on a zero padding result to obtain a first channel impulse response;
- setting a threshold, and finding a plurality of paths in the first channel impulse response according to the first channel impulse response and the threshold;
- and
- calculating a mean square error (MSE) when each path in the first channel impulse response serves as a first path, and setting the path with a minimum mean square error (MMSE) as the first path.
A fine symbol timing synchronization apparatus in an orthogonal frequency division multiplexing (OFDM) system, comprising:
- a channel frequency response calculation circuit, with an input end coupled to an input end of the fine symbol timing synchronization apparatus, for receiving a plurality of first frequency domain symbol signals, extracting a plurality of scattered pilots from the first frequency domain symbol signals, calculating a plurality of first channel frequency responses according to the scattered pilots, and performing an interpolation on the first channel frequency responses to generate a second channel frequency response;
- a storage circuit, with an input end coupled to an output end of the fine symbol timing synchronization apparatus, for storing one of the first frequency domain symbol signals, wherein the stored first frequency domain symbol signal is corresponding to the second channel frequency response;
- an inversed fast Fourier transformer, with an input end coupled to an output end of the storage circuit, for performing a zero padding operation on the second channel frequency response, and performing an inversed fast Fourier transform (IFFT) after the zero padding operation to obtain a first channel impulse response;
- a channel impulse response calculation circuit, with an input end coupled to an output end of the inversed fast Fourier transformer, having a threshold to find a plurality of paths in the first channel impulse response according to the first channel impulse response and the threshold;
- and
- a mean square error (MSE) calculation and comparison circuit, with an input end coupled to the channel impulse response calculation circuit and an output end coupled to an output end of the fine symbol timing synchronization apparatus, for calculating an MSE of each path when each path in the first channel impulse response serves as a first path, and setting the path with a minimum mean square error (MMSE) as the first path.
Dependencies are inferred from the claim text.